The invention relates to a motor vehicle door latch containing a locking mechanism, an actuating lever assembly that acts on the locking mechanism and a drive unit for at least one lever of the actuating lever assembly, in which the drive unit contains at least one motor and a bolt acted upon by the motor.
The lever of the actuating lever assembly acted on by the drive unit is often a locking lever and, in particular, a central locking lever. Such locking levers or central locking lever are generally pivoted by means of an eccentric control journal engaging in a respective fork-shaped recess of the central locking lever (see for instance DE 102 40 003 A1).
A generic motor vehicle door latch according to DE 10 2004 011 798 B3 provides a motorized closing and opening aid for a motor vehicle door. This contains a first output element, acting as a closing aid, which pivots the catch as part of the locking mechanism from its pre-ratchet position into a main ratchet position. A second output element acts as an opening aid and lifts the respective pawl off the catch. As a result, the released catch can be pivoted back to its open position by the force of a spring.
Both output elements are arranged on a common output gear. When turning the output gear in one rotation direction, the first output element is effective, whilst the second output element is ineffective and vice versa. The second output element acting as an opening aid is a longitudinally moveable bolt.
A further state of the art disclosed in DE 196 10 708 A1 describes a door securing unit for motor vehicles. This is located in the immediate vicinity of a locking pin of motor vehicle doors and can be controlled by means of an electric impulse. For this purpose, an electric motor is provided in a housing with one or more locking pins being assigned to the electric motor. The locking pin contains a gear rack section meshing with a toothed gear, acted upon by the motor. In this way, the locking pin can be linearly moved out of the housing.
In drive units with at least one motor and a bolt of the aforementioned design that is acted on by the motor, in particular in an embodiment containing a toothed rod and pinion engaging therein, the problem occurs that radial forces act or can act on the pinion and the bolt or the toothed rod. Such radial forces do, for instance, arise when the movement of the bolt is impeded (by friction) or if the bolt moves against a stop. The overall result can be that the pinion no longer meshes with the teeth of the toothed rod. Depending on the stressing or number of duty cycles this can result in damage of the tooth flanks or even tooth fracturing. This may cause malfunctioning of the drive unit and thus of the entire motor vehicle door latch.
Given the described problems, efforts are currently being made to manufacture and mesh the pinion and toothed rod with the lowest possible tolerances. Furthermore, efforts are made to increase the stiffness of the meshing elements, to exclude most or at least as far as possible any of the described deformation generated by the radial forces. This results in higher manufacturing costs, which is a problem given the enormous cost pressure in the manufacture of motor vehicle accessories. The invention aims to provide a solution for this.